Another Noisy Rearend Problem

[69-er]

This one's a puzzler...

I installed a Richmond gear set, (I know they're typically noisy), in a passenger Chevy 12 bolt and after 200 miles the rearend has become very noisy during coasting. Most of the driving has been around town below 45MPH. A few short, somewhat hard runs have been made under this speed, with easy shifts. At 200 miles, I took it on the highway at 60 MPH for 30 minutes two times. The first run in the morning I could hear a whine when coasting. The second run in the afternoon it became more of a howl than a whine. It's very "obnoxious", even over the loud exhaust.

The differential cover temp was 160 degrees after the second run. I used a magnet in the drain pan and found several metal bits, smaller than a grain of sand, more like a course grit. After letting the oil settle for a day I emptied the pan and fished some more in the "sludge". All that was on the magnet was very fine filings, which is what I would expect. No more bits of metal.

Richmond specifies the backlash at .010". I am getting very close to that with maybe .001"-.002" variation at three places on the ring gear. The carrier bearing races have a slightly frosted appearance.

On the gear patterns, the drive side is a little towards the top and close to the toe. It's somewhat of a thin pattern. The coast side is a wide pattern, maybe a little towards the top, centered between the toe and heel.

I guess the pattern could be just slightly deeper, but I can't understand why it's so noisy, I mean REAL noisy. I was wondering if the gears were going to make it home.



I've learned that coast/deceleration noises are related to the pinion. Before I removed the pinion the preload was at 15 in/lbs. with the seal installed and the carrier out. It had an ever so slight "rough" feeling, exactly like I would expect for bearings that are tightly adjusted. The pinion bearing races also have a frosted look but I can see a diagonal pattern. It's very smooth; I can't feel anything with my fingernail or knife blade edge.

Bottom line is that if this rear wasn't making noises and I was tearing into it just to inspect it, I would say everything is good. With noise I was getting I was expecting to see severe damage, especially with the small amount of metal bits I found.

WTH am I missing???!!!

Thanks!

Larry

[bryant]

what you describe is to little pinion depth. it doesnt take much to be noisy. also its weak to have to little pinion depth. you need to put more pinion depth shim in. get it concentrated in the center.